1. Field of the Invention
The present invention relates to shift operation of a vehicle having a manual transmission including an input-side sub-transmission (splitter) and an output-side sub-transmission (range).
2. Description of Related Art
Some heave trucks include a main transmission provided with a sub-transmission for switching between high and low, and such a sub-transmission includes a splitter on the input side and a range on the output side.
A manual transmission for heavy trucks and the like of a type provided with a splitter and a range is operated with a shift lever and a switch for gear-shifting, and so such an operation for gear-shifting is very complicated as compared with so-called “passenger cars”.
For instance, if a driver erroneously performs operation (erroneous shift operation) to shift to a gear stage on a lower-speed side in spite of the intention to shift to gear on a higher-speed side (e.g., shift to first in spite of the intention of shifting from third to fourth), the rotation speed becomes too high (over-rotation, overrun), and in the worst scenario, the engine or drive-system components may be broken.
On the other hand, if a driver erroneously performs operation to shift to a gear stage on a higher-speed side in spite of the intention to shift to gear on a lower-speed side (e.g., shift to sixth in spite of the intention of shifting from fourth to third), the rotation speed becomes too low (underrun) and falls below the idle rotation speed, and engine stall may happen.
Other conventional techniques include a technique for detecting all gear stages with the gear position switches to prevent over-rotation (e.g., see Japanese Patent Application Laid-open Publication No. 2001-248720). Such a technique, however, is targeted to a vehicle equipped with an automatic transmission, and cannot be used for a vehicle equipped with a manual transmission.